Abstract: The invention relates to complexes comprising a B class ephrin and a PDZ domain containing protein; peptides that interfere with the interaction of a B class ephrin with a PDZ domain binding site, and a PDZ domain containing protein; and, uses of the peptides and complexes. Methods for modulating the interaction of a B class ephrin and a PDZ domain containing protein, and methods for evaluating compounds for their ability to modulate the interaction are also described.

Abstract: A peptide of the formula (I): X.sup.1 -A.sup.1 -A.sup.2 -X.sup.2 -Asn-X.sup.3 -X.sup.4 -P.Tyr-X.sup.5 -X.sup.6 -X.sup.7 -X.sup.8, wherein X.sup.1 represents Lys, Arg, His, Ser, Thr, Tyr, Asn, Leu, Val or Glu, A.sup.1 represents Trp, Leu, Ala, Ser, Ile, Glu, Met, Gly, Cys, Phe, Pro or Val, and A.sup.2 represents Ala, Val, Leu, Ile, Ser, Met, Phe, Gly, Cys, Trp or Pro, X.sup.2 represents Glu, Asn, Tyr, Thr, Ser, Asp or Ile, X.sup.3 represents Pro, Met, Trp, Phe, Ala, Lys, Val, Leu, Ile, Gly or Ser, X.sup.6 represents Ser, Thr, Tyr, Asn, Glu, Met, Ala, Leu, Val or Gly, X.sup.7 represents Asp, Glu, Ala, Val, Leu, Ile, Gly, Cys, Phe, Trp, Met, Pro, Ser or Asn and X.sup.8 which may be present or absent represents Phe, Trp, Pro, Leu, Ala, Val, Ile, Gly, Cys, Met, Asp, Ser or Arg which interferes with the interaction of a PTB domain containing protein with a PTB domain binding site, and truncations and analogues of the peptide.